window.onload = function () {
    (function () {
        let inputNumberEle = document.querySelector('.inputNumber');
        let minus = inputNumberEle.firstElementChild;
        let plus = inputNumberEle.lastElementChild;
        let numberVal = minus.nextElementSibling;
        let num = 1;
        //减一
        minus.addEventListener('click', function () {
            if (--num < 1) {
                num = 1;
                this.style.disabled = true;
            }
            numberVal.value = num;
        })
        //加一
        plus.addEventListener('click', function () {
            num++;
            numberVal.value = num;
        })

        //改变输入框值
        numberVal.addEventListener('change', function () {
            if (isNaN(this.value)) {
                alert('请输入数字');
            } else {
                num = this.value;
            }
        })
    })()
}